Touch display power management in a multi-display device

ABSTRACT

Power management logic of a multi-display touch device provides for selectively reducing a power state of a touch system within each individual display at times when the touch system of the display is inactive. The power management logic facilitates selective toggling of the touch system from a high power state to a low power state independent of a power state of other touch systems in the multi-display device, The power management logic further facilitates selective toggling of the touch system power state from the low power state to the high power state responsive to a communication received across the interlink.

BACKGROUND

Display operation is power intensive, particularly when touch sensing issupported. As such, multi-display touch devices present unique powerchallenges. While designs that reduce power consumption are generallyfavorable across the electronics industry, this is especially true formobile devices with limited battery lives.

SUMMARY

The described technology includes power management logic that reducesbattery consumption in a multi-display touch device. The powermanagement logic is separately executed by a first touch controllerwithin a first display and by a second touch controller within a seconddisplay. The power management logic provides for operating a touchsystem in each display to selectively toggle the touch system in thedisplay from a high power state to a low power state independent of apower state of the touch system in the other display, and to selectivelytoggle the power state of the touch system in the display from the lowpower state to the high power state responsive to a communicationreceived across the interlink.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

Other implementations are also described and recited herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example multi-display device that supportsselectable operation of touch system hardware within different displaysin the same or different power states.

FIG. 2 illustrates architecture of an example multi-display device thatsupports selectable operation of touch controllers in different displaysin a controller-independent power mode and in a controller-unified powermode.

FIG. 3 illustrates first and second exemplary action sequences that maybe implemented by a power management system to support communicationsbetween touch controllers in a multi-display device that supportsselectable operation of touch controllers in either a controller-unifiedpower mode or a controller-independent power mode.

FIG. 4 illustrates an example cycle of processing operations for a touchcontroller in a multi-display touch device implementing the hereindisclosed touch system power management logic.

FIG. 5 illustrates a flow diagram of example power management logicoperations that provide for transitioning a display touch system betweenpower modes in a multi-display system implementing the disclosedtechnology.

FIG. 6 illustrates an example computing device that includes multipledisplays and that supports controller-independent and controller-unifiedpower modes for touch controllers within each of the multiple displays.

DETAILED DESCRIPTIONS

In a mobile device, a significant portion of battery resources are usedto support display operation and touch sensing. Some newer mobiledevices entering the market have multiple touch screens. These designspresent significant challenges in terms of power management and batterylife longevity. Some of these multi-display products are designed tosupport user modes where the user may selectively interact with a singledisplay. In these scenarios, significant power savings could be realizedby implementing a hardware and logic infrastructure that permits thedisplay that not in use to be operated in a different, lower power statethan the display that is in use. For example, the lower power state maysave power by disabling certain features such as touch sensors and/or byslowing the clock rate of the display.

The herein disclosed technology provides a control architecture andpower management system that collectively enable the concurrentoperation of different displays in different power states within amulti-display device. This disclosed control architecture includesmultiple touch controllers that independently implement power managementlogic in different displays of a multi-display device. Notably,concurrent operations of displays in different power modes presents anumber of challenges relating to display responsiveness, such as how toachieve smooth tracking between delays and mitigate power modetransition times. These challenges are uniquely addressed by the hereindisclosed power management logic, which supports touch controlleroperation in each of a controller-unified power mode and acontroller-independent power mode, each of which can provide forselective toggling of the associated touch controller between a highpower state and a low power state.

In the controller-unified power mode, the user is provided with theexperience of interacting with one large screen spanning the differentdisplays instead of two separate screens (e.g., a left-most portion ofthe screen appearing on a left-most display and a right-most portion ofthe display appearing on a right-most display). Activities for bothtouch systems are managed according to a common activity cycle. Duringactive times within the activity cycle, the touch system is operated ina high power state supports full display functionality and highperformance cross-display tracking.

In the controller-independent power mode, the user is provided with theexperience of two independent display screens rather than a unifiedsingle-screen experience. In this mode, the touch systems of the twodisplays may be managed according to different activity cycles andoperated in different power states for periods of time spanning severalminutes or longer. Routine operation of the controller-independent modemay, for example, provide for operating the touch system of one displayin a high power state (e.g., with all functionalities enabled) whileconcurrently operating the touch system of another display in a lowpower state in which touch sensing is disabled. Notably, the low powerstate still supports cross-controller (display-to-display)communications.

According to one implementation, the disclosed power management logicprovides for operating an associated display touch system in a highpower state whenever the associated touch controller is active and forreducing the power state of the display touch system at times when thetouch controller is inactive and expected to remain in inactive for along enough time to support power state toggling (e.g., down, and thenup again in time for the next scheduled activity). As used herein, atouch controller is said to be “active” when performing events, such asevents to scan for or process user inputs or events to process otherreceived communications. A touch controller is, in contrast, “inactive”when turned on but not performing any processing actions, such as duringidle periods within each clock cycle when there are no scans beingperformed or inputs being processed. At times when the touch controlleris not receiving power, it is said to be “off,” which is different from“inactive” as defined above. Examples of active and inactive times arediscussed in greater detail with respect to FIG. 4 .

In one implementation, the low power state is driven by a slower clockcycle than the high power state to save power. In at least oneimplementation, touch sensing is disabled in the low power state but thedisplay remains illuminated. At times when a display is in the highpower state but becomes inactive, the associated touch controller mayselectively lower the clock rate of the associated display and may alsodisable certain features, such as the touch sensing hardware, to savepower. The low power state still supports communications with the otherdisplay(s) in the device. When a communication is received at a touchcontroller operating in the low power state from a touch controller in ahigh power state, the display in the low power state is immediatelytransitioned to the high power state.

In one implementation, the above-described power state transition fromthe low power state to the high power state entails altering a clockrate of the display in the low power state to match the clock rate ofthe display in the high power state. Selectively lowering a power stateof one display independent of the other at inactive times savessignificant power resources. At the same time, the operation of theclock cycles at the higher rate in the high power mode ensures messagesare not dropped whenever the displays are communicating with oneanother.

In one implementation, the multiple displays may be powered “off” andpowered “on” in unison when operating in the controller-unified powermode; however, power state transitions in the controller-independentpower mode are limited to those power states that support cross-displaycommunications (e.g., from low power mode to high power mode and viceversa but not into or out of the “off” state). This feature ensures anacceptably fast response time, as it is much quicker to transition adevice from the low power state to the high power state than it is totransition in and out of an “off” state. These and other benefits may berealized from the following figures.

FIG. 1 illustrates an example multi-display device 100 that supportsselectable operation of touch system hardware within different displays102 and 104 in the same or different power states. Although themulti-display device 100 includes two displays, it may be appreciatedthat the herein disclosed power management technique are extendible tomulti-display systems with three or more displays without substantialmodification. In FIG. 1 , the multi-display device 100 is a mobiledevice, such as the size of a tablet or a mobile phone. The displays 102and 104 are connected to one another by a hinge 116 and adapted to pivotrelative to one another about the hinge. In one implementation, thehinge 116 permits the user to rotate the displays 102 and 104 through afull range of relative angles such that that the two displays 102 and104 can be parallel and stacked on top of one another or at any positionup to 180 degrees apart. In other implementations, the displays of themulti-display device 100 do not rotate relative to one another.

View B of FIG. 1 illustrates an exemplary hardware architecture of themulti-display device 100. Specifically, each of the two displays 102 and104 includes an associated touch controller 108 and 110, respectively.The touch controllers 108 and 110 control power to touch sensinghardware (e.g., pen or finger touch inputs), such as a digitizer,capacitive sensors, or other touch-sense technology and executeprocessing logic for detecting and processing touch inputs and forconveying sensed touch inputs to a host 112. The host 112 may likewisetransmit communications to either of the touch controllers 108 and 110,such as messages to initiate firmware actions for noise reduction in thesensed data.

The host 112 may be a system-on-chip (Soc) as shown, anapplication-specific integrated circuit (ASIC), central processing unit(CPU), or other processing system. In FIG. 1 , the host 112 is shownintegrated within (e.g., internal to the device casing of) the display102. However, in other implementations, the host 112 may be at alocation that is external to the displays 102 and 104.

In FIG. 1 , the host 112 is shown directly coupled to the touchcontroller 108 of the display 102 but is indirectly coupled to the touchcontroller 110 within the display 104. As used herein “direct coupling”refers to a coupling that is between two processing endpoints withoutgoing through an intermediary processing entity. In contrast, an“indirect coupling” implies a coupling that is between two processorswith a third processor in between, acting as an intermediary. In FIG. 1, the touch controller 110 is indirectly coupled to the host 112 in thatit communicates with the host 112 through the touch controller 108rather than through an independent communication channel bypassing thetouch controller 108. In other implementations, the various displays mayassume any physical arrangement relative to one another and the systemhost.

An interlink 114 provides an electrical interface that supportsbidirectional communications between the touch controllers 106 and 108.According to one implementation, each of the touch controllers 108 and110 implements identical power management logic that provides foroperating the associated display touch system in either (1) acontroller-independent power mode or (2) a controller-unified powermode.

In the controller-unified power mode, a same virtual screen may bepresented across the first display 102 and the second display 104,giving the user the “feel” of interacting with a single large screenrather than two separate screens. In one implementation, the touchcontrollers 106 and 108 perform pre-scheduled processing activitiesaccording to a same, pre-selected activity cycle when operating in thecontroller-unified power mode. One example of a touch controlleractivity cycle is given by FIG. 4 herein, which illustrates variousactivities such as “pen search” (searching for pen input) “touch search”(searching for finger-touch input).

The two displays 102 and 104 are said to be in the controller-unifiedpower mode whenever the two touch controllers 106 and 108 are performingprocessing activities according to the same activity cycle andpresenting data across the two displays 102 and 104 in a unified mannerthat gives the user the feel of interacting with a single screen.

In contrast, the touch systems of the two displays 102 and 104 are saidto be in the controller-independent power mode whenever the touchcontrollers 106 and 108 are concurrently operating according todifferent activity cycles and presenting data on the two displays 102,104 that resembles two different screens (e.g., the user has the feel ofinteracting with two different screens). Transitions between thecontroller-unified power state and the controller-independent powerstate may occur responsive to detection of the device in in a certainphysical orientation or responsive to user inputs (e.g., button push).

In either the controller-unified power mode or thecontroller-independent power mode, a touch controller (106 or 108) mayselectively toggle the associated touch system between a low power stateand a high power state. The low power state differs from the high powerstate in that certain display functionality is disabled to save power.While the touch system is not completely off (e.g., aspects of the touchsystem IC chip are still powered and the display is still illuminated),features such as touch sensing may be disabled.

In the controller-unified mode, the two touch systems may be maintainedjointly in the high power state a vast majority of the time. In someimplementations, a touch controller operating in the unified-power modemay be permitted to independently drop the power state of its associatedtouch system from the high power state to the low power state for brief(e.g., sub-second) idle windows within the common activity cycle sharedby both touch systems. This concept is discussed with respect to FIG. 4.

When operating in the controller-independent power mode, the two touchcontrollers 106 and 108 concurrently implement different activity cyclesand may independently reduce the power state of the associated touchsystem from the high power state to the low power state for moreextended periods of time, such as time periods that span severalactivity cycles of the other touch controller that is concurrentlyoperating in the high power state.

In one implementation, the touch controllers 108 and 110 each performroutine processing actions according to an activity cycle driven by aninternal clock. A frequency of the clock is slowed in the low powerstate as compared to the high power state in order to save power. Forexample, the touch system clock may operate at 20 MHz in the high powerstate and at 18 MHz in the low power state. In addition to this lowerclock frequency, hardware components, such as touch sensors, may also beturned off in the low power state to save additional power.Consequently, touch input sensing may be supported in the high powerstate but disabled in the low power state.

In both of the low power state and the high power state, communicationsare supported across the interlink 114 in the sense that alltransmitters and receivers of the touch controllers 108 and 110 are onand capable of receiving and transmitting data.

When a message arrives across the interlink 114, it is desirable toprocess the message quickly to release an associated buffer (e.g., adirect memory access (DMA) buffer) so that the next incoming message canbe received. However, message processing is performed more slowly in thelow power state because the low power state is driven by a clock ratethat is slowed as compared to the high power state. When a receivedmessage is processed too slowly and the buffer is not freed up in timeto receive a next incoming message, there exists a risk that nextincoming message may be dropped. In some systems, this is referred to asDMA buffer overflow.

To prevent DMA buffer overflow, all data communications between the twotouch controllers 108 and 110 are, in one implementation, proceeded byan interrupt signal that may be sent in either direction. If a touchcontroller is not already operating in the high power state at the timethat it detects an interrupt signal that has been transmitted across theinterlink 114, the detection of the interrupt signal causes the touchcontroller to begin transitioning from the low power state to the highpower state. Data communications may be transmitted between thecontrollers after the power state transition is partially or fullycomplete, e.g., pursuant to various requirements discussed below.

In one implementation, the herein disclosed power management logic isdesigned to ensure that the touch controllers 108, 110 do not send datamessages across the interlink 114 when in the low power state and do notreceive messages across the interlink 114 at times when the clock ratesof the two touch controllers 106, 108 are different (e.g., when the twotouch controllers 106, 108 are operating in different power states).According to one implementation, sending a data message across theinterlink 114 entails a sequence of operations including (1) sending aninterrupt signal across the interlink 114; (2) determining, based on thetransmitted signal, what power state the receiving touch controller isoperating in; (3) if the receiving touch controller is operating in thelower power state, initializing a power state transition process thatincludes resetting the clock of the receiving touch controller; and (4)timing transmission of the data message to ensure that receipt of themessage across the interlink 114 occurs after the clock cycle of thereceiving display has been reset to match that of the touch controllerthat transmitted the data message. Exemplary operations consistent withthe above logic are presented with respect to FIG. 3 .

The power management logic implemented by each the touch controllers106, 108 provides for transitioning from the high power state to the lowpower state when operating in either the controller-unified mode or thecontroller-independent one whenever time permits—meaning, whenever thetransition can be accomplished without interrupting any scheduledactivities of the currently-implemented activity cycle for the givenmode. For example, a touch controller operating in the high power statewith a cycle repeated every 10 ms may selectively transition theassociated touch system into the low power state for a time periodspanning an idle portion of the cycle (e.g., the last 4 ms) where noactivities are scheduled to be performed by the touch controller,provided that the touch system can be transitioned back to the highpower state in time for the next scheduled touch controller activity.Further examples of this are discussed with respect to FIG. 4 and FIG. 5.

FIG. 2 illustrates architecture of an example multi-display device thatsupports selectable operation of touch controllers in different displaysin a controller-independent power mode and in a controller-unified powermode. The device 200 includes a first display 202, a second display 204,and a host 206 (e.g., an SoC or ASIC) that acts as a central processingsystem for the device 200. The first display 202 includes a first touchcontroller 212 and the second display 204 include a second touchcontroller 214. The first display 202 is directly coupled to the host206 and the second display 204 is indirectly coupled to the host 206through an interlink 218 and through the first display 202.Consequently, the first touch controller 212 effectively acts as a“master controller” while the second touch controller 214 acts as a“slave controller” in the sense that its communications to the host 206all first past through the master device, as shown.

The touch controllers 212 and 214 may each be understood as comprisinghardware and/or software components that are adapted to control hardwarewithin an associated touch system. For example, the touch controllers212 and 214 each include a microprocessor that executes firmwaresequences to detect touch inputs from touch sensors of the associateddisplay as well as to perform certain processing on detected touchinputs. In one implementation, the touch system of each display 202 and204 is self-contained on an integrated circuit (e.g., an IC thatincludes both a touch controller and the touch system hardware that itcontrols).

In FIG. 2 , each of the displays further includes a communicationinterface 208 and 210 that implements a designated network protocol tocommunicate with the device host 206. However, due to the master/slavearrangement of FIG. 2 , the communication interface 210 is used for allhost communications and the communication interface 210 is unused. Theinterlink 218 includes transmitters and receivers. Although not shown,the touch controllers 212, 214 may each include memory (e.g., buffers)for temporary data storage.

According to one implementation, the touch controllers 212 and 214execute power management logic to independently operate their respectivehardware in two different selectable power modes—a controller-unifiedpower mode and a controller-independent power mode, both with featuresthe same or similar to those described above with respect to FIG. 1(e.g., full/unified screen v. split/non-unified screen). Within eitherof the selectable power modes, the touch controller may elect to togglethe associated touch system from a high power state or a low powerstate.

When both touch systems are operated in the high power state, the clocksof the touch controllers 212 and 214 operate at a same clock rate. Alltouch controller functionality is enabled for both displays. When one ofthe touch systems is selectively toggled into the low power state, itsclock cycle is lowered and certain functionality, such as touch sensing,is disabled. Two different clock rates concurrently drive the associatedtouch controllers when the touch controllers are concurrently operatingin different power states,

When one of the touch controller 212 and 214 is inactive (e.g., notperforming any processing operations), the touch controller mayselectively and independently transition its associated touch systemfrom high power state to the low power state. When this occurs, thetouch controller independently drops its clock rate down from the higherrate to the lower rate to save power. In one implementation, the touchcontrollers 212 and 214 also disable touch sensors (e.g., turn offcertain touch-sense hardware components) when operating in the low powerstate to save power. At the same time, the receivers and transmitters ofthe interlink 218 are all kept in the on state in the low power state toenable a faster transition back to the high power state than would berealized if the entire touch controller 212 or 214 in the low powerstate were instead turned off. To transition from the low power state tothe high power state, the clock rate of each of the touch controllers212 and 214 is reset to the higher frequency cycle by using a PLLstabilization process.

To conceptually illustrate the above, assume that the slave device(touch controller 214) is operating in the high power state while themaster controller (touch controller 212) is operating in the low powerstate. In this case, touch sensing hardware is enabled for the display204 but disabled for the display 202. When the user touches the screenof slave device (with either a stylus or finger), this triggers an eventmessage to the host 206 to inform the host of the location of touchinputs and to allow the host 206 to convey inputs back to the display204, such as to update what is being shown on the display 204.

If the slave controller tries to send a message to the host 206 acrossthe interlink 218 while continuing to operate in thecontroller-independent power mode, there exists a risk that the messagemay be dropped (and lost) by the master controller operating in the lowpower state due to message buffer overflow that may occur when incomingmessages are processed at the slower clock rate. For this reason, bothtouch controllers may implement logic to time the transmission of datacommunications in a manner that ensures messages are received across theinterlink 218 exclusively at times that the receiving controller isoperating according to the higher clock rate of the high power state.

As used herein, a “data communication” refers to a communication withmultiple bits or data packets encoding data. In one implementation, atouch controller sends an interrupt signal across the interlink 218prior to each data communication. Receipt of the interrupt signal at theother touch controller causes the receiving touch controller to initiatea clock rate transition from the slower clock rate of the low powerstate to a higher clock rate of the high power state (unless thereceiving controller is already operating at the higher clock rate).Although the interrupt signal is a type of communication, it isdifferent than the “data communication” defined above in that is not amulti-bit communication. In one implementation, the interrupt is asignal state change transmitted by flipping the polarity of a signalthat transmitted across the interlink 218.

For example, both of the touch controllers 212, 214 may listen to aninter-link change HW state and, when this state changes, this isinterpreted as an “interrupt” that may initiate a power state changetransition if the device detecting the interrupt is operating in the lowpower state. If the receiving touch controller (in the above example,the master) detects the interrupt while operating in the high powerstate, no power transition is necessary to ensure that thesoon-to-be-transmitted data communication will not be dropped. If,however, the receiving touch controller detects the interrupt whileoperating in the low power state, the receiving touch controllerimmediately initiates a sequence of actions—beginning with a clockreset—to self-transition from the low power state to the high powerstate.

The touch controller preparing to send a data communication across theinterlink 218 implements logic to time the transmission of the datacommunication so as to ensure that the other touch controller has time,following receipt of the interrupt, to transition to the faster clockrate before the data communication is received. For example, thetransmission can performed at the earliest possible transmission timefor which it can be assured that receipt of the data communication willoccur after the clock reset on the other touch controller.

The example described above pertains to the scenario where the slavecontroller is trying to send a data communication to the host throughthe master controller. However, identical or similar logic may likewisebe implemented in the reverse scenario where the master controller istrying to send a data communication to the slave controller. Forinstance, the master controller may, prior to sending a datacommunication across the interlink 218, transmit an interrupt across theinterlink 218. If the slave device touch system is operating in the lowpower state when it receives the interrupt, the touch controller of theslave device immediately begins to transition to the high powerstate—beginning with the clock reset. The data communication istransmitted at the earliest possible time for which it can be guaranteedthat receipt of the data communication occurs after the clock reset iscompleted.

A more complete sequence of operations illustrating the above isdescribed and shown with respect to FIG. 3 .

FIG. 3 illustrates first and second exemplary action sequences 302 and304 that may be implemented by a power management system to supportcommunications between touch controllers in a multi-display device thatsupports selectable operation of touch controllers in either acontroller-unified power mode or a controller-independent power mode.

According to one implementation, the action sequences 302, 304 areperformed in a dual-display device that has features consistent withthose described above with respect to either of FIG. 1 or 2 . The actionsequences 302, 304 represent different sequences of actions that may beperformed (in the alternative) each time a data communication (“MSG” inthe figure) is transmitted from a touch controller operating in a highpower state to a touch controller operating in a low power state.

The two example sequences different in that the action sequence 302 isless efficient than the action sequence 304 and is shown primarily tohelp illustrate key communication challenges that arise when independenttouch controllers are concurrently driven by different clock rates. Theaction sequence 304, in contrast, illustrates an alternative way ofaccomplishing the same operations shown with respect to the actionsequence 302 that improves device performance by decreasing perceivablelag time between the provisioning of user inputs to a display and thecorresponding response of that display (e.g., display update).

In the device corresponding to the example of FIG. 3 , touch inputs aredetectable in a high power state but not in a low power state. Thedisabling of touch sensors and associated circuitry when operating inthe low power state (e.g., at inactive times) saves significant devicepower. When operating in the high power state, the touch controllers aredriven according to a higher clock rate that a clock rate that is usedto drive the low power state. Both of the exemplary action sequences302, 304 correspond to the scenario where a data communication is to betransmitted from a touch controller operating in the high power state toa touch controller that is operating in a low power state. To ensurethat the communication is not dropped, actions are taken reset the clockrate of the touch controller in the low power state before thecommunication arrives.

The action sequence 302 is initiated at a time t1 when a first touchcontroller detects an event triggering the transmission of a datacommunication across the interlink to a second touch controller. Forexample, the first touch controller may detect a touch input thattriggers transmission of select information to a device host that is topass through the second touch controller in route to the host (e.g., asin the master/slave architecture of FIG. 2 ). Alternatively, the firsttouch controller may detect another type of event that triggerstransmission of a message to the other touch controller, such as ahardware error that triggers transmission of a debug message.

Responsive to detecting the event triggering the communication, thefirst touch controller transmits an interrupt signal at t2. In oneimplementation, the interrupt signal is an inter-link change hardwarestate that the second controller is listening to across the interlink.The interrupt signal is an effective way for one touch controller to“signal” to the other because (as described elsewhere herein) datacommunications may be dropped when the two touch systems are operatingin different power modes. The interrupt signal therefore serves thepurpose of a data communication but is transmitted more quickly andwithout risk of being dropped.

The second touch controller detects the interrupt while operating in thelow power state and immediately self-initiates a process fortransitioning from the low power state to the high power state. Thistransition includes operations that include powering on touch sensorsand associated circuitry as well as resetting the clock rate of thefirst touch controller to match and be synchronized with the higherclock rate of the second touch controller. This transition from thelower power state to the higher power state may span a considerablylengthy time interval that is on the order of 250 μs, as shown betweent2 and t3.

Once the power state transition is complete (at t3), the first touchcontroller sends the data communication across the interlink to thesecond touch controller. The time between transmission (at t3) andreceipt (at t4) of the data communication spans another considerablylengthy time interval, such as 100 μs. By the time the second controllerreceives the data communication, over 350 μs have elapsed. Thissignificant elapsed time translates to lag time that may be perceived bya user, such as when the user provides a touch input and waits for thedisplay to update in response.

The action sequence 304 presents an alternative and more efficient orderfor the operations described above. At a time t1, the first touchcontroller detects an event triggering the transmission of a datacommunication across the interlink (e.g., a message to the SoC or to theother data controller) and transmits an interrupt. At t2, the secondtouch controller detects the interrupt while operating in the low powerstate and immediately begins the process of transitioning from the lowpower state to the high power state.

The operations in the action sequence 304 differ from those describedabove with respect to prioritization of tasks performed as part of thetransition from the low power state to the high power state. In theaction sequence 304, the touch controller splits the power statetransition into two temporal components including a first subset oftasks performed prior to transmission of the message (e.g., between t3and t4) and a second subset of tasks performed after transmission of themessage (e.g., between t5 and t6). As described below, the splitting ofthese tasks in this manner effectively allows the data communication tobe transmitted earlier—and without a risk of being dropped—than in theabove-described scenario pertaining to the action sequence 302. Quickertransmission of the data communication translates to a reduction indevice responsive times that may be apparent to an end user.

When the interrupt is detected by the second touch controller, thesecond touch controller begins the first subset of operations byinitializing a PLL stabilization process. The PLL stabilization iseffective to reset the clock of the second touch controller to match thehigher clock rate of the first touch controller. This PLL stabilizationprocess can be completed within a predefined time interval that is, inthe illustrated example, ˜70 μs. In the action sequence 304, the datacommunication is transmitted across the interlink by the first touchcontroller at the “earliest possible time”—meaning, the earliest time atwhich it can be assured that the arrival of the communication at thesecond controller is timed to be after the completion of the PLLstabilization (after t3) and preferably, as close in temporal proximityto the completion of the PLL stabilization as possible.

In the device corresponding to the example of FIG. 3 , transmission ofthe data communication takes just longer than the PLL stabilizationprocess. In this case, the data communication transmission spans ˜80 μswhereas the PLL rest takes 70 μs. Consequently, the data communicationcan be transmitted at the same time that the PLL stabilization isstarted (t2), and it can be assured message arrival occurs after the PLLstabilization is complete. In other implementations, the datacommunication may be sent earlier or later provided that the datacommunication is still received after completion of the PLLstabilization and timed to be as close in time as possible followingcompletion of the PLL stabilization process.

Once the PLL stabilization is complete (e.g., at t3), the clocks on thetwo touch controllers are again operating at the faster clock rate,which ensures that the data communication is not dropped. The PLLstabilization completes at t3, and the data communication arrives at t4.When the data communication is received at t4, message processing takespriority and the second controller temporarily halts all processingactivities. This effectively postpones a subset of remaining power statetransition tasks until after the data communication is placed into astorage buffer. When the data communication is safely in the buffer thetouch controller can, at t5, resume the postponed power state transitiontasks and thereby finish transitioning the touch system of the seconddisplay to the high power state. Once all power state transition tasksare completed (e.g., at t6) the second touch controller may thenretrieve the stored communication from the buffer and process thecommunication.

When the second touch controller is finally ready to process thereceived communication (at t6), approximately 250 μs have elapsed sincethe transmission of the interrupt signal. Therefore, the operations ofthe action sequence 304 are completed about 100 μs quicker than theoperations of the action sequence 302. The translates to higher deviceresponsiveness and a much lower likelihood of the user noticing lagtimes associated with provisioning of touch inputs.

FIG. 4 illustrates an example cycle 400 of processing operations thatmay be implemented by a touch controller in a multi-display implementingthe herein disclosed touch system power management logic. The cycle 400provides one example schedule of processing activities that may becyclically-executed within a set interval (e.g., 10 ms) by an associatedtouch controller such as any of the individual touch controllersdiscussed with respect to FIG. 1-3 . For example, each touch controllerof the various multi-display devices disclosed herein may execute itsown respective processing activities according to a cycle similar inconcept to that shown in FIG. 4 .

The cycle 400 may be understood as driving activities of thecorresponding touch controller and being repeatedly executed (in a loop)until such time that the touch controller is powered off or until thecycle 400 is swapped for another stored cycle. For example, each touchcontroller may have access to multiple different cycles stored infirmware and selectively alternate which of the stored cycles isfollowed at different times based on various factors such as the typesof inputs being provided by a user, the amount of reserve battery powerremaining, the identities and characteristics of other active processeson the multi-display device, etc.

The cycle 400 is 10 ms in length and provides for performing a number ofprocessing activities in a high power state. Various activities includedin the cycle include Touch Track (TT, a scan to detect finger-touchinputs); noise search (NS, a calibration to detect noise that may besubtracted from detected touch signals); Dual Search (DS, an activitythat searches for finger-touch and pen inputs simultaneously); PenSearch (PS, an activity that searches for pen input); and TouchProcessing (an activity that provides for processing detected touchinputs before transmitting related data to a host).

As explained with respect to other figures herein, the touch controllermay be configured to selectively toggle between a low power state thatdoes not support touch sensing (e.g., touch sensing hardware is poweredoff) and a high power state that does support touch sensing. In oneimplementation, all of the exemplary activities shown in the cycle 400can be performed in the high power mode but not in the low power state.

When all touch controllers in the device are implementing a sameactivity cycle, such as the cycle 400, the touch controllers are said tobe operating in a “controller-unified” mode. When the touch controllersare implementing different cycles (e.g., cycles associated withdifferent power states and clock rates), the touch controllers are saidto be operating in a “controller-independent mode.”

During each repeated cycle (e.g., the cycle 400 or other alternative,selectable cycles), the touch controller identifies idle window(s)within the cycle that are large enough to facilitate a temporarily(e.g., few millisecond) reduction in the power state from the high powerstate to the low power state. The term “idle window” refers to windowswithin the processing cycle where the touch controller is not scheduledto perform any processing activities. An idle window may be large enoughto support a temporary reduction in the power state when it is longenough in duration to allow the touch system to reduce the power statefrom high to low and to restore the high power state before the plannedstart time of the next cycle activity.

Assume, for example, it takes 30 microseconds to reduce from the highpower state to the low power state and 250 microseconds to increase thepower state from the low power state back to the high power state. Inthis case, an idle window of 280 microseconds is needed to support atemporary reduction in the power state. In the cycle 400, there doesexist an idle window 402 that is about 3 milliseconds in duration. Sincethis is larger than 250 microseconds, this idle window is identified asbeing large enough to support a power reduction. At the start time ofthe idle window 402, the touch controller initiates a power statereduction event (e.g., spanning 30 microseconds). The touch controllersubsequently initiates power state increase event toward the end of theidle window, such as at or near the last possible start time for whichit can be assured that the power state increase events will be completedprior to the start of the next scheduled activity. For example, thetouch controller may initiate the power state increase at a time that is250 microseconds before the end of the idle window, allowing the firsttouch track (TT) activity in the cycle to be started performed on time.

In this way, the touch controllers in the multi-display device canindependently reduce the power state of the associated touch system forshort (sub-second) intervals within their respective activity cycleswhenever there exists an idle window long enough to ensure the powerstate can be reduced and then restored without interrupting anyprocessing activities. The net effect of these sub-second reduced-powerintervals is significant over an extended period of time such as an houror a few hours, meaningfully extending battery life.

Notably, FIG. 4 provides an example of a scenario when the differenttouch controllers may concurrently operate in different power states(high/low) while implementing the same prescheduled activity cyclecharacteristic of the unified-controller mode. This occurs when one ofthe two touch controllers has a larger idle window than the other (e.g.,due to lack of user touch/pen inputs) that allow it to drop into thelower power state for a brief time interval within the activity cycle,as described above. In this case, the touch controllers are said to beoperating in the controller-unified mode (due to the common activitycycle) even though the respective power state is different for a briefperiod of time.

FIG. 5 illustrates a flow diagram of example power management logicoperations 500 that provide for transitioning a display touch systembetween power states in a multi-display system implementing thedisclosed technology. The multi-display system includes a first touchdisplay with touch sensing hardware (e.g., digitizer, capacitancesensors) managed by a first touch controller and a second touch displaywith touch sensing hardware managed by a second touch controller. Eachof the first touch controller and the second touch controller mayindependently implement the power management logic operations 500 toselectively transition the associated display touch system between ahigh power (HP) state and a low power (LP) state independent of powertransitions that may or may not be performed by the other touchcontroller.

Whenever both touch controllers are operating in the high power state,the internal clocks of the two controllers are operating a same, fasterrate and touch sensing is enabled on both displays. Whenever one of thetwo touch controllers transitions from the high power state to the lowpower state, the controller operating at the LP state is driven by aclock rate that is lower than the clock rate driving the othercontroller that continues to operate in the HP state.

The operations 500 (logic executed by each of the touch controllers)provides a set of continuous and repeated checks to determine if andwhen power transitions may occur. Operations shown inside of the graybox 520 may be performed when the associated touch controller isoperating in the LP state. Operations shown outside of the gray box 520may be performed when the associated touch controller is operating inthe HP state. Notably, the illustrated operation flow is cyclical andthe operations could therefore be understood as starting at any pointwithin the flow diagram.

Per the operations 500, the touch controller can selectively andindependently reduce power of the associated touch system whenever timepermits—meaning, for example, whenever there exists an idle windowbetween planned activities of the touch controller that is large enoughto support two power state transitions (from HP to LP and then back toHP).

A determination operation 502 determines whether there exists anupcoming idle window in the current activity cycle of the touchcontroller that is large enough to allow a temporary reduction in thetouch system power state (to LP) while still allowing the touchcontroller to return to the HP state in time for the next scheduledactivity that requires the HP state.

The “idle window” referenced in the determination operation 502 refersto a continuous window of time in which the touch controller is notscheduled to perform any activities that require the HP state (forexample, touch scans may be supported by the HP state but unsupported bythe LP state). If, for example, it takes 30 microseconds to transitionfrom the HP state to the LP state and another 250 microseconds totransition back to the HP state, the determination operation 510 maydetermine that the idle window is of “sufficient duration” whenever theidle window is greater than 280 microseconds in duration. Provided suchan idle window is identified, a transitioning operation 504 transitionsthe touch system from the HP state to the LP state at the start of theidentified idle window.

If there are no idle windows of sufficient size to support the abovedescribed power state transitions in the current cycle (e.g., down to LPand then back again to HP within a few milliseconds), a waiting loop 514is entered until such time that an idle window of sufficient duration isidentified by the determination operation 502.

Following the transition operation 504, a detection operation 506listens for an interrupt signal from the other touch controller. Forexample, the interrupt detection operation may detect the interrupt whena state change is detected on an input signal provided by the othertouch controller. In one implementation, interrupt signals of thisnature are transmitted by the touch controller each time the touchcontroller detects an event triggering a prospective data communicationaction to the other touch controller. Prior to sending that datacommunication, the touch controller sends an interrupt signal. If thetouch controller receiving the interrupt signal is not currentlyoperating in the HP state, detection of the interrupt signal may causethe touch controller to initiate a transition from the current LP stateto the HP state. If an interrupt is detected at the detection operation506, a transitioning operation 512 transitions the touch system from theLP state back to the HP state, which ensures that the touch controlleris available to receive and process data communications received fromthe other touch controller.

Returning to the interrupt detection operation 506: if no interrupt isdetected, the touch system remains in the LP state and the operationsproceed to a determination operation 508, which determines whether thetime remaining in the idle window is less than a defined a threshold.For example, the determination operation 508 may determine that the timeremaining is greater than the threshold if the remaining idle windowtime exceeds (e.g., by some defined margin) the time that is required toincrease the touch system power state from low to high. The thresholdmay be set to ensure that the remaining time in the idle window is longenough to increase the touch system power state from LP to HP withoutrunning into the next scheduled activity.

If the time remaining is greater than the threshold, the touch systemmay remain in the low power state while the interrupt detectionoperation 506 and the determination operation 508 are cyclicallyrepeated until an interrupt is detected or a planned activity requiringthe HP state is scheduled to occur within the examined future timeinterval.

If the determination operation 508 determines that the time remaining inthe idle window is less than the threshold, a transitioning operation512 commences and begins transitioning the touch system from the LPstate to the HP state (e.g., where the internal clocks of the two touchcontrollers operate at the faster clock rate). After this power statetransition is compete, the determination operation 502 is repeated toidentify the next idle window in the activity cycle that may support apower state reduction and the other operations 500 are therebycyclically repeated.

FIG. 6 illustrates an example computing device 600 with multipledisplays 622 that supports controller-independent and controller-unifiedpower modes and power state independence for touch controllers withineach of the multiple displays. The computing device 600 may be a clientdevice, such as a laptop, mobile device, desktop, tablet, or aserver/cloud device. The computing device 600 includes one or moreprocessor(s) 602, and a memory 604. The memory 604 generally includesboth volatile memory (e.g., RAM) and nonvolatile memory (e.g., flashmemory). An operating system 610 resides in the memory 604 and isexecuted by the processor(s) 602.

In an example computing device 600, as shown in FIG. 6 , one or moremodules or segments, such as applications 650; all or part of acommunication interface, touch controllers, data controllers, and othermodules are loaded into the operating system 610 on the memory 604and/or storage 620 and executed by processor(s) 602. The storage 620 maystore timing data, sensor measurements, and other data and be local tothe computing device 600 or may be remote and communicatively connectedto the computing device 600.

The computing device 600 includes a power supply 616, which is poweredby one or more batteries or other power sources and which provides powerto other components of the computing device 600. The power supply 616may also be connected to an external power source that overrides orrecharges the built-in batteries or other power sources.

The computing device 600 may include one or more communicationtransceivers 630, which may be connected to one or more antenna(s) 632to provide network connectivity (e.g., mobile phone network, Wi-Fi®,Bluetooth®) to one or more other servers and/or client devices (e.g.,mobile devices, desktop computers, or laptop computers). The computingdevice 600 may further include a network adapter 636, which is a type ofcommunication device. The computing device 600 may use the adapter andany other types of communication devices for establishing connectionsover a wide-area network (WAN) or local-area network (LAN). It should beappreciated that the network connections shown are exemplary and thatother communications devices and means for establishing a communicationslink between the computing device 600 and other devices may be used.

The computing device 600 may include one or more input devices 634 suchas that a user may enter commands and information (e.g., a keyboard ormouse). These and other input devices may be coupled to the server byone or more interfaces 638, such as a serial port interface, parallelport, or universal serial bus (USB). The computing device 600 furtherincludes the displays 622, which are touch screen displays incorporatingtouch sense hardware. In one implementation the displays 622 eachfurther include at least one microprocessor and memory storing firmwareinstructions for detecting and interpreting touch inputs provided to thetouch sense hardware.

The computing device 600 may include a variety of tangibleprocessor-readable storage media and intangible processor-readablecommunication signals. Tangible processor-readable storage can beembodied by any available media that can be accessed by the computingdevice 600 and includes both volatile and nonvolatile storage media,removable and non-removable storage media. Tangible processor-readablestorage media excludes intangible communications signals (such assignals per se) and includes volatile and nonvolatile, removable, andnon-removable storage media implemented in any method or technology forstorage of information such as processor-readable instructions, datastructures, program modules, or other data. Tangible processor-readablestorage media includes, but is not limited to, RAM, ROM, EEPROM, flashmemory or other memory technology, CDROM, digital versatile disks (DVD)or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage, or other magnetic storage devices, or any othertangible medium which can be used to store the desired information andwhich can be accessed by the computing device 600. In contrast totangible processor-readable storage media, intangible processor-readablecommunication signals may embody processor-readable instructions, datastructures, program modules, or other data resident in a modulated datasignal, such as a carrier wave or other signal transport mechanism. Theterm “modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, intangiblecommunication signals include signals traveling through wired media suchas a wired network or direct-wired connection, and wireless media suchas acoustic, RF, infrared, and other wireless media.

According to one implementation, an example mobile device disclosedherein includes a first touch controller in a first display; a secondtouch controller in a second display; an interlink coupling the firsttouch controller to the second touch controller; and power managementlogic. The power management logic is separately executed by each of thefirst touch controller and the second touch controller and is executableto operate a touch system in each display to selectively toggle thetouch system in the display from a high power state to a low power stateindependent of a power state of the touch system in the other displayand to selectively toggle the power state of the touch system in thedisplay from the low power state to the high power state responsive to acommunication received across the interlink. The above features arebeneficial because the independent management of the two touch systemsallows an idle one of the two touch systems to be transitioned to a lowpower state to save power while the other touch system remains active.

In example mobile device according to any preceding mobile device, thetouch inputs are detectable in the high power state but not in the lowpower state. Disabling touch sensors in the low power state allowsfurther power savings.

In another example mobile device of any preceding mobile device, thepower management logic is further executable to operate the first touchcontroller and the second touch controller in each of acontroller-unified mode and a controller-independent mode. A sameactivity cycle is concurrently executed by the first touch controllerand the second touch controller when operating in the controller-unifiedmode and different activity cycles are concurrently executed by thefirst touch controller and the second touch controller when operating inthe controller-independent mode.

In yet still another example mobile device of any preceding mobiledevice, the First touch controller and the second touch controller areconcurrently driven by different clock rates when the first touchcontroller is operating in the low power state and the second touchcontroller is operating in the high power state.

In still another example mobile device of any preceding mobile device,the power management logic is further executable by each touchcontroller of the first touch controller and the second touch controllerto selectively and independently transition the associated touch systemto the low power state during each idle window within a scheduledactivity cycle that is large enough in duration to support a transitioninto and out of the low power state.

In yet still another example mobile device of any preceding mobiledevice, the power management logic is further executable to transmit aninterrupt signal each time an event triggers transmission of a datacommunication between the first touch controller and the second touchcontroller; listen for the interrupt signal when operating in the lowpower state; and responsive to detection of the interrupt signal,selectively transition the touch system out of the low power state ofand into the high power.

In yet still another example mobile device of any preceding mobiledevice, selectively transitioning the touch system further comprisesdividing power state transition tasks into a first subset of tasksincluding a clock reset and a second subset of tasks including poweringon touch sensors and prioritizing the first subset of tasks ahead of thesecond subset of tasks.

In another example mobile device of any preceding mobile device, thefirst display acts as a master device that communicates with a host bytransmitting data across a first interface and wherein the seconddisplay acts as a slave device that communicates with the host bytransmitting data across the interlink, through the first display, andacross the first interface.

In yet another aspect, some implementations include a computer-readablestorage medium for storing computer-readable instructions. Thecomputer-readable instructions, when executed by one or more hardwareprocessors, perform power management operations in a dual display deviceconsistent with any of the features described herein.

In yet still another aspect, some implementations include methods forimplementing power management logic in a dual display mobile. Whenperformed, the operations of the recited methods provided thefunctionality of any of the computer system features described herein.

Some implementations may comprise an article of manufacture. An articleof manufacture may comprise a tangible storage medium to store logic.Examples of a storage medium may include one or more types ofcomputer-readable storage media capable of storing electronic data,including volatile memory or nonvolatile memory, removable ornon-removable memory, erasable or non-erasable memory, writeable orre-writeable memory, and so forth. Examples of the logic may includevarious software elements, such as software components, programs,applications, computer programs, application programs, system programs,machine programs, operating system software, middleware, firmware,software modules, routines, subroutines, operation segments, methods,procedures, software interfaces, application program interfaces (API),instruction sets, computing code, computer code, code segments, computercode segments, words, values, symbols, or any combination thereof. Inone implementation, for example, an article of manufacture may storeexecutable computer program instructions that, when executed by acomputer, cause the computer to perform methods and/or operations inaccordance with the described embodiments. The executable computerprogram instructions may include any suitable types of code, such assource code, compiled code, interpreted code, executable code, staticcode, dynamic code, and the like. The executable computer programinstructions may be implemented according to a predefined computerlanguage, manner or syntax, for instructing a computer to perform acertain operation segment. The instructions may be implemented using anysuitable high-level, low-level, object-oriented, visual, compiled,and/or interpreted programming language.

The implementations described herein are implemented as logical steps inone or more computer systems. The logical operations may be implemented(1) as a sequence of processor-implemented steps executing in one ormore computer systems and (2) as interconnected machine or circuitmodules within one or more computer systems. The implementation is amatter of choice, dependent on the performance requirements of thecomputer system being utilized. Accordingly, the logical operationsmaking up the implementations described herein are referred to variouslyas operations, steps, objects, or modules. Furthermore, it should beunderstood that logical operations may be performed in any order, unlessexplicitly claimed otherwise or a specific order is inherentlynecessitated by the claim language.

What is claimed is:
 1. A mobile device comprising: a first touchcontroller in a first display; a second touch controller in a seconddisplay; an interlink coupling the first touch controller to the secondtouch controller; power management logic separately executed by each ofthe first touch controller and the second touch controller, the powermanagement logic being executable to operate a touch system in eachdisplay to: selectively toggle the touch system in the display from ahigh power state to a low power state independent of a power state ofthe touch system in the other display; and selectively toggle the powerstate of the touch system in the display from the low power state to thehigh power state responsive to an interrupt received across theinterlink, the interrupt being a signal state change corresponding toreversal in polarity of a signal transmitted across the interlink. 2.The mobile device of claim 1, wherein touch inputs are detectable in thehigh power state but not in the low power state.
 3. The mobile device ofclaim 2, wherein the power management logic is further executable tooperate the first touch controller and the second touch controller ineach of a controller-unified mode and a controller-independent mode,wherein a same activity cycle is concurrently executed by the firsttouch controller and the second touch controller when operating in thecontroller-unified mode and different activity cycles are concurrentlyexecuted by the first touch controller and the second touch controllerwhen operating in the controller-independent mode.
 4. The mobile deviceof claim 2, wherein the first touch controller and the second touchcontroller are concurrently driven by different clock rates when thefirst touch controller is operating in the low power state and thesecond touch controller is operating in the high power state.
 5. Themobile device of claim 1, wherein the power management logic is furtherexecutable by each touch controller of the first touch controller andthe second touch controller to selectively and independently transitionthe associated touch system to the low power state during each idlewindow within a scheduled activity cycle that is large enough induration to support a transition into and out of the low power state. 6.The mobile device of claim 2, wherein the power management logic isfurther executable to: transmit an interrupt signal each time an eventtriggers transmission of a data communication between the first touchcontroller and the second touch controller; listen for the interruptsignal when operating in the low power state; and responsive todetection of the interrupt signal, selectively transition the touchsystem out of the low power state of and into the high power.
 7. Themobile device of claim 6, wherein selectively transitioning the touchsystem further comprises: dividing power state transition tasks into afirst subset of tasks including a clock reset and a second subset oftasks including powering on touch sensors; and prioritizing the firstsubset of tasks ahead of the second subset of tasks.
 8. The mobiledevice of claim 1, wherein the first display acts as a master devicethat communicates with a host by transmitting data across a firstinterface and wherein the second display acts as a slave device thatcommunicates with the host by transmitting data across the interlink,through the first display, and across the first interface.
 9. One ormore non-transitory computer-readable storage media encodingcomputable-executable instructions for executing a computer process, thecomputer process comprising: executing power management logic at adisplay controller executed by a first touch controller of a firstdisplay and a second touch controller of a second display, the powermanagement logic being executable to operate a touch system in eachdisplay to: selectively toggle the touch system in the display from ahigh power state to a low power state independent of a power state ofthe touch system in the other display; and selectively toggle the powerstate of the touch system in the display from the low power state to thehigh power state responsive to an interrupt received across an interlinkcoupling the first touch controller to the second touch controller, theinterrupt being a signal state change corresponding to reversal inpolarity of a signal transmitted across the interlink.
 10. The one ormore non-transitory computer-readable storage media of claim 9, whereintouch inputs are detectable in the high power state but not in the lowpower state.
 11. The one or more non-transitory computer-readablestorage media of claim 10, wherein the power management logic is furtherexecutable to operate the first touch controller and the second touchcontroller in each of a controller-unified mode and acontroller-independent mode, wherein a same activity cycle isconcurrently executed by the first touch controller and the second touchcontroller when operating in the controller-unified mode and differentactivity cycles are concurrently executed by the first touch controllerand the second touch controller when operating in thecontroller-independent mode.
 12. The one or more non-transitorycomputer-readable storage media of claim 10, wherein the first touchcontroller and the second touch controller are concurrently driven bydifferent clock rates when the first touch controller is operating inthe low power state and the second touch controller is operating in thehigh power state.
 13. The one or more non-transitory computer-readablestorage media of claim 10, wherein executing the power management logicfurther comprises selectively and independently transitioning from thehigh power state to the low power state during each idle window of ascheduled activity cycle that is large enough in duration to support atransition into and out of the low power state.
 14. The one or morenon-transitory computer-readable storage media of claim 10, whereinexecuting the power management logic further comprises: transmitting aninterrupt signal each time an event triggers transmission of a datacommunication between the first touch controller and the second touchcontroller; listening for the interrupt signal when operating in the lowpower state; and responsive to detecting the interrupt signal,selectively transitioning the touch system out of the low power stateand into the high power state.
 15. The one or more non-transitorycomputer-readable storage media of claim 14, wherein selectivelytransitioning the touch system further comprises: dividing power statetransition tasks into a first subset of tasks including a clock resetand a second subset of tasks including power on touch sensors; andprioritizing the first subset of tasks ahead of the second subset oftasks.
 16. A mobile device comprising: a master touch controller in afirst display, the master touch controller being directly coupled to ahost within the mobile device; a slave touch controller in a seconddisplay, the slave touch controller being indirectly coupled to the hostthrough the master touch controller of the first display; an interlinkcoupling the master touch controller to the slave touch controller;power management logic separately executed within each of the mastertouch controller and the slave touch controller, the power managementlogic being executable to operate a touch system in each display to:selectively toggle the touch system in the display from a high powerstate to a low power state independent of a power state of the touchsystem in the other display; and selectively toggle the power state ofthe touch system in the display from the low power state to the highpower state responsive to an interrupt received across the interlink,the interrupt being a signal state change corresponding to reversal inpolarity of a signal transmitted across the interlink.
 17. The mobiledevice of claim 16, wherein touch inputs are detectable in the highpower state but not in the low power state.
 18. The mobile device ofclaim 17, wherein the power management logic is further executable tooperate the first touch controller and the second touch controller ineach of a controller-unified mode and a controller-independent mode,wherein a same activity cycle is concurrently executed by the firsttouch controller and the second touch controller when operating in thecontroller-unified mode and different activity cycles are concurrentlyexecuted by the first touch controller and the second touch controllerwhen operating in the controller-independent mode.
 19. The mobile deviceof claim 16, wherein the slave touch controller and the master touchcontroller when the slave touch controller is operating in the low powerstate and the master touch controller is operating in the high powerstate.
 20. The mobile device of claim 17, wherein the power managementlogic is further executable by each touch controller of the slave touchcontroller and the master touch controller to selectively andindependently transition the associated touch system from the high powerstate to the low power state during each idle window within a scheduledactivity cycle that is large enough in duration to support a transitioninto and out of the low power state.